Iodine is necessary for the synthesis of which hormone?
(a) Adrenaline
(b) Thyroxin
(c) Auxin
(d) Insulin
Explanation: The thyroid gland secretes the hormone thyroxine or T4 into the bloodstream. The major function of the thyroid gland is to produce thyroid hormones required by the body for metabolism. Iodine is required to make thyroid hormone. If iodine is not available in the diet, the thyroid gland may produce an insufficient amount of hormone. Hence, (b) is the correct option.